BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to trocar assemblies. More particularly, the invention relates to a circumferential trocar sealing structure.

2. Description of the Prior Art

A trocar assembly is a surgical instrument that is used to gain access to a body cavity. A trocar assembly generally comprises two major components, a trocar sleeve, composed of a trocar housing and a trocar cannula, and a trocar obturator. The trocar cannula, having the trocar obturator inserted therethrough, is directed through the skin to access a body cavity. Once the body cavity is accessed, laparoscopic or arthroscopic surgery and endoscopic procedures may be performed. In order to penetrate the skin, the distal end of the trocar cannula is placed against the skin that has been previously cut with a scalpel and the trocar obturator is used to penetrate the skin and access the body cavity. By applying pressure against the proximal end of the obturator, the sharp point of the obturator is forced through the skin until it enters the body cavity. The trocar cannula is inserted through the perforation made by the trocar obturator and the trocar obturator is withdrawn, leaving the trocar cannula as an access way to the body cavity.

The proximal end portion of the trocar cannula is typically joined to a trocar housing that defines a chamber having an open distal end portion in communication with the interior lumen defined by the trocar cannula. An obturator, or other elongate surgical instruments or tools, axially extend into and are withdrawn from the trocar cannula through the proximal end portion of the chamber defined by the trocar housing.

Current trocar assemblies are commonly designed with a seal mechanism positioned within the chamber of the trocar housing. The sealing mechanisms are commonly a sealing grommet or gasket through which the obturator or other instruments extend. The sealing mechanism seals against the outer surface of the inserted instruments and thereby prevents fluids and insufflation gas from leaving or entering the body cavity through the trocar cannula. It is desired that such seals provide for good tear resistance, resistance to snagging and low friction with respect to insertion of a device such as a rod, shaft or cylinder.

Seal assemblies are designed to maintain a seal before the insertion of an instrument and after the removal of the instrument. As a result, many trocar assemblies provide double sealing systems. That is, a top, or proximal, seal is used to seal around the tool/instrument when present and a flapper door or duckbill seal is requited below the top seal for sealing the trocar cannula when the instrument is not present.

In contrast, other trocar assemblies employ a single sealing mechanism. Many of these trocar seal assemblies simply employ a silicone seal with a small hole slightly smaller than the smallest tool/instrument to be used in conjunction with the trocar assembly. This type of seal is often referred to as a lip seal. Surgical instruments of various diameters are passed through the lip seal. As such, these seals are often required to provide a seal for use with a full range of instruments. The opening diameter of the seals is, therefore, small relative the largest diameter instruments.

In fact, it is not uncommon for lip seals to be pushed to 400% strain. By forcing these large diameter instruments through a relatively small diameter lip seal, these large diameter instruments are subjected to a significant increase in the normal force upon the instrument shaft. The surgeon feels this increased force as increased drag or resistance to instrument insertion/movement. It is also required that the material properties of the seal be such that the seal does not rip or tear as the seal is stretched to its limit. As a result, a need currently exists for an improved trocar seal assembly overcoming the deficiencies of the prior art.

The present invention overcomes these deficiencies by providing a seal assembly which eliminates the hoop/high stress issues associated with prior art seals and provides a seal assembly which may be utilized either as a single sealing method (reducing the overall complexity of the trocar) or as a proximal seal assembly in a multiseal system.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide a seal assembly adapted for use in conjunction with a trocar assembly. The seal assembly includes a plurality of seal segments. Each seal segment includes a peripheral edge and a seam edge. At least a first seal segment and a second seal segment are connected along their respective peripheral edges to form a first seal layer having a seam defined by the seam edge of the first seal segment and the seam edge of the second seal segment. At least a third seal segment and a fourth seal segment are connected along their respective peripheral edges to form a second seal layer having a seam defined by the seam edge of the third seal segment and the seam edge of the fourth seal segment. The seam of the first seal layer has a first longitudinal axis and the seam of the second seal layer has a second longitudinal axis, and the first seal layer is oriented relative to the second seal layer such that the first longitudinal axis is angularly oriented relative to the second longitudinal axis.

It is also an object of the present invention a trocar assembly including a trocar cannula having a proximal end and distal end. The trocar assembly further includes a trocar housing coupled to the proximal end of the trocar cannula for receiving and guiding an obturator through the trocar cannula. The trocar housing includes an open proximal end portion defining an opening provided with a seal assembly. The seal assembly is constructed as described

Other objects and advantages of the present invention will become apparent from the following detailed description when viewed in conjunction with the accompanying drawings, which set forth certain embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded view of a trocar assembly in accordance with the present invention.

FIG. 2 is an exploded view of the seal assembly in accordance with the embodiment disclosed in FIGS. 3, 4 and 5.

FIG. 3 is an exploded perspective view of first and second seal segments in accordance with the present invention.

FIG. 4 is a perspective view of a seal layer composed of the first and second seal segments shown in FIG. 3.

FIG. 5 is a cross sectional view of the seal layer shown in accordance with FIG. 4.

FIG. 6 is an exploded perspective view of a further embodiment of first and second seal segments.

FIG. 7 is a perspective view of a seal layer composed of the first and second seal segments shown in FIG. 6.

FIG. 8 is a cross sectional view of the seal layer shown in accordance with FIG. 7.

FIG. 9 is a perspective view of an alternate embodiment of a seal layer composed of first and second seal segments in accordance with a further embodiment.

FIG. 10 is an exploded perspective view of the first and second seal segments shown in accordance with FIG. 9.

FIG. 11 is a cross sectional view of the seal layer along the line 11-11 of FIG. 9.

FIG. 12 is perspective view of a seal layer in accordance with a further embodiment.

FIG. 13 is an exploded perspective view of the first and second seal segments shown in accordance with FIG. 12.

FIG. 14 is a cross sectional view of the seal layer along the line 14-14 of FIG. 12.

FIG. 15 is a perspective view of a seal layer in accordance with still another embodiment.

FIG. 16 is an exploded perspective view of the first and second seal segments shown in accordance with FIG. 15.

FIG. 17 is a cross sectional view of the seal layer along the line 17-17 of FIG. 15.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The detailed embodiments of the present invention are disclosed herein. It should be understood, however, that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, the details disclosed herein are not to be interpreted as limiting, but merely as the basis for the claims and as a basis for teaching one skilled in the art how to make and/or use the invention.

With reference to FIGS. 1, 2, 3, 4 and 5, a seal assembly 10 for a trocar assembly 12 is disclosed. The seal assembly 10 provides for improved resistance to tearing by reducing the likelihood for tenting to occur. As those skilled in the art will appreciate, tenting occurs when a seal is stretched and thinned out, for example, by an instrument passing through the seal, thus providing an area of weakness which may be easily punctured. As those skilled in the art will certainly appreciate, the present seal assembly 10 is adapted for use with a variety of trocar assemblies 10.

Apart from the seal assembly 10 in accordance with the present invention, the general structure of trocar assembly 12 does not form part of the present invention. For example, and by way of explaining the present seal assembly 10, the trocar assembly 12 may take a variety of forms without departing from the spirit of the present invention.

With that in mind, and by way of example, the trocar assembly 12 includes a trocar cannula 14, a trocar obturator 16 and a trocar housing 18. The trocar cannula 14 defines an interior lumen having an open distal end portion and an open proximal end portion. The proximal end portion extends into and is mounted in the distal end portion of trocar housing 18. The trocar housing 18 has an open proximal end portion that defines an opening 20. The opening 20 is provided with a proximal seal assembly 10 constructed in accordance with the present invention and described in detail hereinbelow. The opening 20 is further provided with a duckbill seal assembly 22 positioned beneath the proximal seal assembly 10. While the present seal assembly 10 is disclosed as a proximal seal assembly 10 forming part of a dual sealing system, the present seal assembly may be utilized in a single seal system without departing from the spirit of the present invention.

The trocar obturator 16 is slidably and removably extendable within the trocar cannula 14 and is inserted into the trocar housing 18 and the trocar cannula 14 through the proximal seal assembly 10, the duckbill seal assembly 22 and the opening 20 of the trocar housing 18. An obturator handle 24 is provided at the proximal end of the trocar obturator 16 and a sharpened point or blade (not shown) is formed at the distal end thereof. As is well known in the art, the seal assembly 10 cooperates with the trocar obturator 16, or another surgical instrument extending through the trocar cannula 14, to sealingly engage the outer surface thereof and thereby preclude the passage of fluids through the trocar housing 18.

With reference to the various embodiments in accordance with the present invention, the proximal seal assembly 10 is composed of multiple overlapping seal segments 26 a, 26 b, 26 a′, 26 b′ assembled so as to minimize leakage between the seal assembly 10 and the insertable rod, shaft or collar of various instruments. In particular, four seal segments 26 a, 26 b, 26 a′, 26 b′ are arranged to create the seal body 28 of the seal assembly 10. While four seal segments are utilized in accordance with a preferred embodiment of the present invention, the seal assembly may ultimately be formed with different numbers of seal segments without departing from the spirit of the present invention.

With reference to FIG. 2, a preferred embodiment of the present seal assembly 10 is disclosed. The seal assembly 10 employs several radial seal segments 26 a, 26 b, 26 a′, 26 b′ that fold around the shaft of an inserted instrument. In accordance with the proposed embodiment, hoop stress is eliminated by replacing the single hole of a prior art lip seal with multiple circumferentially positioned seal segments 26 a, 26 b, 26 a′, 26 b′. These seal segments 26 a, 26 b, 26 a′, 26 b′, when opened with a round probe, provide sealing similar to that provided by the round hole of a prior art lip seal. The present design also utilizes an angled edge feature for wrapping around an instrument shaft while yielding a design that is both easier to mold and inspect.

As will be discussed below in greater detail, the present seal assembly 10 uses a series of interlocking seal segments 26 a, 26 b, 26 a′, 26 b′. The preferred embodiment disclosed herein employs four seal segments 26 a, 26 b, 26 a′, 26 b′, although more than four seal segments may be utilized without departing from the spirit of the present invention. All four seal segments 26 a, 26 b, 26 a′, 26 b′ are molded individually and then assembled into the final configuration.

The hoop stress of the present seal assembly 10 is reduced by providing a single seal assembly 10 with multiple layers, that is, seal segments 26 a, 26 b, 26 a′, 26 b′, lapped over each other in a manner creating a through hole. The layers form contact zones with the inserted probe. The sum of the contact zones provides contact around the full diameter of the inserted instrument. Without a probe inserted, the seal segments 26 a, 26 b, 26 a′, 26 b′ remain in contact with each other so that the seal assembly 10 allows for no air passage.

The proximal seal assembly 10 is composed of a seal body 28 constructed from two seal layers 34, 34′ respectively composed of a pair of seal segments 26 a, 26 b, 26 a′, 26 b′. Once the two seal layers 34, 34′ are properly constructed, the second seal layer 34′ is placed beneath the first seal layer 34 with the seal seam 36′ of the second seal layer 34′ rotated 90° from the seal seam 36 of the first seal layer 34. In this way, the seal seams 36, 36′ of the first and second seal layers 34, 34′ create a double seamed seal providing for improved circumferential sealing within the trocar housing 18.

Apertures 37, 37′ are formed along a peripheral edges 35 a, 35 b, 35 a′, 35 b′ of the respective seal segments 26 a, 26 b, 26 a′, 26 b′ and are spaced such that the apertures 37, 37′ will align when the seal layers 34, 34′ are properly aligned and rotated 90 degrees. As such, a male retaining ring 44 and a female retaining ring 46 are positioned on opposite sides of the juxtaposed first and second seal layers 34, 34′. The male retaining ring 44 includes a series of connecting prongs 45 that extend through the apertures 37, 37′ of the seal layers 34, 34′ and are connected with the female openings 47 formed in the female sealing ring 46. In this way, the seal body 28 composed of the first and second seal layers 34, 34′ is securely positioned between the male and female retaining rings 44, 46, and ultimately supported for attachment to the trocar housing 18.

FIG. 2 illustrates an embodiment wherein a seal assembly 10 is provided with seal layers 34, 34′ comprising seal segments 26 a, 26 b, 26 a′, 26 b′. In accordance with this embodiment, the seal segments 26 a, 26 b, 26 a′, 26 b′ leaves no center hole. It is believed this arrangement provides for the best sealing prior to insertion and after removal of the rod. However, and in accordance with an alternate embodiment, an optional clearance opening 127, such as shown in FIGS. 6, 7 and 8, may be utilized.

In practice, when a device such as rod or shaft is inserted through the seal assembly 10, the overlapping segments of the first and second seal layers 34, 34′ deflect both downward and around the device inserted. This deflection creates a cat-eye effect on the first seal layer 34, leaving gaps between the inserted device and the first and second seal segments 26 a, 26 b making up the first seal layer 34. The second seal layer 34′, with its seam 36′ rotated 90° from the seam 36′ of the first seal layer 34′, counters the gaps between the inserted device and the seal segments 26 a, 26 b of first seal layer 34, creating a circumferential seal around the inserted device.

As will be described below in substantial detail, various embodiments in accordance with the present invention are contemplated. The various embodiments describe the application of the concept underlying the present invention to flat seal segments with straight seam edges, flat seal segments with sigmoidal seam edges, cone shaped seal segments with straight seam edges and cone shaped seal segments with sigmoidal seam edges.

While the present seal assembly 10 is specifically adapted for use in conjunction with trocar assemblies, it will be appreciated by those skilled in the art that the present seal assembly may be employed for different functions without departing from the spirit of the present invention.

With reference to FIGS. 3, 4 and 5, a preferred embodiment of the seal layer 34 is disclosed. This is the same seal layer 34 disclosed with reference to FIG. 2. Each of the seal segments 26 a, 26 b in accordance with this embodiment are semi-circular and flat with straight seam edges 38 a, 38 b. As is shown in FIG. 3, and as described below in greater detail, the use of straight seam edge 38 a, 38 b produces a seal seam 36 that follows along a substantially straight line.

Referring to FIGS. 3, 4 and 5, each of these flat seal segments 26 a, 26 b includes a substantially flat semicircular disk having a substantially round peripheral edge 35 a, 35 b and a straight seam edge 38 a, 38 b, which defines the straight seal seam 36. In accordance with a preferred embodiment of the present invention, the outer peripheral edge 35 a, 35 b of each seal segment 26 a, 26 b defines an arc of approximately 200-220 degrees. The outer peripheral edges 35 a, 35 b further include a series of apertures 37 that function as a means of attachment for the seal segments 26 a, 26 b. The seal segments 26 a, 26 b further include respective tapered angled sections 30 a, 30 b extending radially for connecting adjacent seal segments 26 a, 26 b. The angled sections 30 a, 30 b are respectively tapered on one side. A matching taper 32 a, 32 b is also formed along the underside of each seal segment 26 a, 26 b opposite the angled section 30 a, 30 b. The angled sections 30 a, 30 b of the seal segments 26 a, 26 b allow for increased contact between assembled seal segments.

As mentioned above, the radially extending angled sections 30 a, 30 b are tapered as they extend toward the tip thereof. The underside of each seal segment 26 a, 26 b opposite the angled section 30 a, 30 b is similarly formed with a matching taper 32 a, 32 b to that of the angled section 30 a, 30 b. In this way, the angled section 30 a of the first seal segment 26 a is seated within the matching taper 32 b along the underside of the second seal segment 26 b and the angled section 30 b of the second seal segment 26 b is seated within the matching taper 32 b along the underside of the first seal segment 26 a. The matching tapers 32 a, 32 b permit the formation of a first seal layer 34 including no undesirable ridges or bumps along its underside due to the coupling of the first seal segment 26 a to the second seal segment 26 b.

In practice, and with reference to FIGS. 3, 4 and 5, two seal segments 26 a, 26 b are connected in an overlapping relationship to create a first seal layer 34. As such, the resulting first seal layer 34 defines a complete circular outer periphery with a straight seal seam 36 extending between the first and second seal segments 26 a, 26 b. As will be discussed below, the shape of the seam edges 38 a, 38 b of the seal segments 26 a, 26 b ultimately defines the shape of the seal seam 36 extending between the first and second seal segments 26 a, 26 b making up the first seal layer 34.

As was mentioned above, the concepts underlying the present invention may be practiced through the utilization of a variety of seal layer constructions without departing from the spirit of the present invention. Some of these contemplated constructions are disclosed below. Since it is believe those skilled in the art will appreciate the seal layer will be assembled in a manner similar to that described above with reference to FIG. 2, the details of constructing the complete seal assembly are not be repeated and the following disclosure focuses upon the construction of the individual seal layers.

With reference to FIGS. 6, 7 and 8, a further embodiment in accordance with the present invention is disclosed. This embodiment is substantially similar to that disclosed with reference to FIGS. 3, 4 and 5, but includes a central clearance opening 127. Each of the seal segments 126 a, 126 b in accordance with this embodiment is semicircular and flat with straight seam edges 138 a, 138 b. As is shown in FIG. 7, and as described below in greater detail, the use of a straight seam edge 138 a, 138 b produces a seal seam 136 that follows along a substantially straight line.

Referring to FIGS. 6, 7 and 8, each of these flat seal segments 126 a, 126 b includes a substantially flat semicircular disk having a substantially round peripheral edge 135 a, 135 b and a straight seam edge 138 a, 138 b which defines the straight seal seam 136. Each seal segment 126 a, 126 b also includes a center clearance recess 127 a, 127 b, which ultimately define the center clearance opening 127.

In accordance with a preferred embodiment of the present invention, the outer peripheral edge 135 a, 135 b of each seal segment 126 a, 126 b defines an arc of approximately 200-220 degrees. The outer peripheral edges 135 a, 135 b further include a series of apertures 137 that function as a means of attachment for the seal segments 126 a, 126 b. The seal segments 126 a, 126 b further include respective tapered angled sections 130 a, 130 b extending radially for connecting adjacent seal segments 126 a, 126 b in the manner discussed above. The angled sections 130 a, 130 b are respectively tapered on one side. A matching taper 132 a, 132 b is also formed along the underside of each seal segment 126 a, 126 b opposite the angled section 130 a, 130 b. The angled sections 130 a, 130 b of the seal segments 126 a, 126 b allow for increased contact between assembled seal segments 126 a, 126 b.

In practice, and with reference to FIGS. 6, 7 and 8, two seal segments 126 a, 126 b are connected in an overlapping relationship to create a first seal layer 134. As such, the resulting first seal layer 134 defines a complete circular outer periphery with a straight seal seam 136 extending between the first and second seal segments 126 a, 126 b. As will be discussed below, the shape of the seam edge 138 a, 138 b of the seal segments 126 a, 126 b ultimately defines the shape of the seal seam 136 extending between the first and second seal segments making up the first seal layer 134.

A further embodiment is disclosed with reference to FIGS. 9, 10, 11. This embodiment relates to a seal layer 234 composed of flat seal segments 226 a, 226 b having sigmoidal seam edges 238 a, 238 b. As is shown in FIG. 10 and is described below in greater detail, the use of sigmoidal seam edges 238 a, 238 b produces a seal seam 236 that is substantially S-shaped. Each of the flat seal segments 226 a, 226 b include a substantially flat semicircular disk having a substantially round peripheral edge 235 a, 235 b and a sigmoidal shaped edge that ultimately defines the seam edge 238 a, 238 b. Ultimately, a seal body employing two of the present seal layer 224 as described above will create a seal assembly with an S-cut seal seam 236.

In accordance with a preferred embodiment of the present invention, the outer peripheral edges 235 a, 235 b of each of the seal segments 226 a, 226 b define an arc of approximately 200-220 degrees. The outer peripheral edges 235 a, 235 b further include a series of apertures 237 that function as a means of attachment for the seal segments 226 a, 226 b. The seal segments 226 a, 226 b further include respective tapered angled sections 230 a, 230 b extending radially for connecting adjacent seal segments 226 a, 226 b in the manner discussed above. A matching taper 232 a, 232 b is also formed along the underside of each of the seal segments 226 a, 226 b opposite the angled sections 230 a, 230 b. The angled sections 230 a, 230 b of the seal segments 226 a, 226 b allow for increased contact between assembled seal segments 226 a, 226 b.

In practice, and with reference to the figures, two seal segments 226 a, 226 b are connected in an overlapping relationship to create a first seal layer 234. As such, the resulting first seal layer 234 defines a complete circular outer periphery with a sigmoidal seal seam 236 extending between the first and second seal segments 226 a, 226 b. As will be discussed below, the sigmoidal shape of the seam edges 238 a, 238 b of the respective seal segments 226 a, 226 b ultimately define the shape of the seal seam 236 extending between the first and second seal segments 226 a, 226 b making up the first seal layer 234.

Still a further embodiment is disclosed with reference to FIGS. 12, 13 and 14. This embodiment relates to a seal layer 334 composed of cone shaped seal segments 326 a, 326 b having straight seam edges 338 a, 338 b. As is shown in the figures and as described below in greater detail, the use of a straight seam edge 338 a, 338 b produces a seal seam 336 that is substantially straight. The cone shaped seal segments 326 a, 326 b each include a cone shaped structure that extends about only a portion of a circle. As such, the cone shaped seal segments 326 a, 326 b may be considered as constituting “a semicircular cone”. Each of the semicircular cones includes a flat, substantially round peripheral edge 335 a, 335 b and a straight seam edge 338 a, 338 b.

In accordance with a preferred embodiment of the present invention, the outer peripheral edge 335 a, 335 b of each of the seal segments 326 a, 326 b defines an arc of approximately 200-220 degrees. The outer peripheral edge 335 a, 335 b further includes a series of apertures 337 that function as a means of attachment for the seal segments 326 a, 326 b. The seal segments 326 a, 326 b further include respective tapered angled sections 330 a, 330 b extending radially for connecting adjacent seal segments 326 a, 326 b in the manner discussed above. A matching taper 332 a, 332 b is also formed along the underside of each of the seal segments 326 a, 326 b opposite the angled portions 330 a, 330 b. The angled portions 330 a, 330 b of the seal segments 326 a, 326 b allow for increased contact between assembled seal segments 326 a, 326 b.

In practice, and with reference to the figures, two seal segments 326 a, 326 b are connected in an overlapping relationship to create a first seal layer 334. As such, the resulting first seal layer 334 defines a complete circular cone with a straight seal seam 336 extending between the first and second seal segments 326 a, 326 b. As will be discussed below, the shape of the seam edge 338 a, 338 b of the seal segments 326 a, 326 b ultimately defines the shape of the seal seam 336 extending between the first and second seal segments 326 a, 326 b making up the first seal layer 334.

Yet a further embodiment is disclosed with reference to FIGS. 15, 16 and 17. This embodiment relates to a seal layer 434 composed of cone shaped seal segments 426 a, 426 b having sigmoidal seam edges 438 a, 438 b. The cone feature of this embodiment reduces the potential for seal inversion upon instrument retraction and provides a natural “lead in” towards the center of the coned seal assembly.

As is shown in FIGS. 15, 16 and 17 and as described below in greater detail, a further embodiment of a seal layer 434 composed of seal segments 426 a, 426 b is disclosed. The use of sigmoidal seam edges 438 a, 438 b produce a seal seam 436 that is substantially S-shaped. Referring to the figures, each of the cone shaped seal segments 426 a, 426 b includes a cone shaped structure that extends about only a portion of a circle. As such, the cone shaped seal segments may be consider as constituting “a semicircular cone”. The semicircular cone includes a flat, substantially round peripheral edge 435 a, 435 b and a sigmoidal shaped edge that defines the seam edge 438 a, 438 b.

In accordance with a preferred embodiment of the present invention, the outer peripheral edges 435 a, 435 b of the seal segments 426 a, 426 b define an arc of approximately 200-220 degrees. The outer peripheral edges 435 a, 435 b further include a series of apertures 437 that function as a means of attachment for the seal segments 426 a, 426 b. The seal segments 426 a, 426 b further include tapered angled sections 430 a, 430 b extending radially for connecting adjacent seal segments 426 a, 426 b in the manner discussed above. A matching taper 432 a, 432 b is also formed along the underside of each of the seal segments 426 a, 426 b opposite the angled sections 430 a, 430 b. The angled sections 430 a, 430 b of the seal segments 426 a, 426 b allow for increase contact between assembled seal segments 426 a, 426 b.

In practice, two seal segments 426 a, 426 b are connected along their respective peripheral edges 435 a, 435 b in an overlapping relationship to create a first seal layer 434. As such, the resulting first seal layer 434 defines a complete circular cone with a seal seam 436 extending between the first and second seal segments 426 a, 426 b. As will be discussed below, the shape of the seam edge 438 a, 438 b of the seal segments 426 a, 426 b ultimately defines the shape of the seal seam 436 extending between the first and second seal segments 426 a, 426 b making up the first seal layer 434.

The cone feature of the seal assembly reduces the possibility of seal inversion upon instrument retraction. Seal inversion can cause binding of the instrument during retraction creating difficulty when removing instruments from the trocar. The cone feature also provides a natural lead in towards the center of the seal assembly. This guides the instrument inserted towards the center of the seal assembly and reduces the potential of puncturing through the seal at location towards the outer periphery of the cone.

In accordance with a preferred embodiment of the present invention, the seal segments are composed of an elastomer or a cross-linked polymer such as, but not restricted to, silicone or a polyisoprene. However, those skilled in the art will appreciate the possibility that other materials may be employed without departing from the spirit of the present invention.

While the preferred embodiments have been shown and described, it will be understood that there is no intent to limit the invention by such disclosure, but rather, is intended to cover all modifications and alternate constructions falling within the spirit and scope of the invention as defined in the appended claims.